Currently, stack technologies (including stack and cluster technologies and the like) are widely applied in data communications devices. In most stack technologies, multiple data communications devices are connected using a data channel such as an Ethernet or a high speed Ethernet data channel to form a stack system. In a stack system established using data channels, there may be merely a data channel between each data communications device and its adjacent data communications device. A data communications device generally includes at least one service board, and each service board includes at least one processor used for service processing.
A communications device generally needs to find a fault itself by means of detection when its adjacent communications device partially or entirely fails, so as to perform corresponding emergency handling in time. Generally, a processor used for service processing in the communications device directly monitors port state of each data channel, and the processor determines, according to a monitoring result, whether the adjacent communications device partially or entirely fails. It is found by practice that an existing mechanism for monitoring whether an adjacent communications device partially or entirely fails generally requires a long time and has low reliability, and therefore cannot satisfy the need of quick troubleshooting.